13. Beneficial Microorganisms

The web of life depends on microorganisms, a vast network of small, unseen
allies that permeate the soil, water, and air of our planet. Many kinds of microorganisms
existed for billions of years before any plants or animals came into
being. Microorganisms created the atmosphere, turned bare rock and lava into
soil, helped plants colonize land, and remain vital to the survival of plants, animals,
and people today.